By Simon Cox
The Investigation, Radio 4
Builders. Nannies. Engineers. Fruit pickers. Hard working Poles have been earning pounds and providing extra labour since 2004. What if they all decide to leave?
This might not get built, for a start
How would Britain cope if the Poles went home? It may seem unlikely but companies across the country are reporting that the Polish influx is coming to an end.
Danny Sriskandarajah, policy director of think tank the Institute for Public Policy Research, says it's something business and Government needs to think about.
"That tap of Polish workers is going to run dry. And I fear that policymakers haven't quite grasped the immense challenge that might bring because if the Poles don't do the jobs, who will?"
This could prove particularly sticky for the construction industry. Poland is investing in big infrastructure projects as it prepares to co-host the 2012 European championships. It is starting to lure back the plumbers and carpenters who have been rebuilding Britain.
Kris Ruszczynski's construction company, Polonia, had 50 builders working on the refit of the Home Office until the end of the year. "There is a shift and it hit me hard, nearly 30% of my team didn't come back after Christmas."
With the zloty rising against the pound, will they stay?
Britain, of course, has its own little bash in 2012. Add to that the Government's commitment to build three million new homes and Crossrail, and that's a lot of builders. The Federation of Master Builders estimates that 87,500 new builders are needed every year for the next five years. If the Poles head for home, it's going to set back major infrastructure projects like the Olympics, says spokesman Bryan Berry. "The bigger problem is that we won't be able to find enough labour."
Pick your own
The effect of a Polish exodus could be even greater for the agricultural sector. Scripps Farm in Kent has seen many seasons of fruitfulness. Their million apple and pear trees supply fruit to some of the biggest supermarkets. All of the fruits have to be picked by hand and for the past four years, managing director James Simpson has relied mainly on Poles.
Last summer that changed. "The Poles and the Czechs weren't knocking on the door the way they were two or three years ago." The farm's Polish contingent is down by a third on previous years, and without them the farm couldn't have expanded.
Will crops rot rather than be picked?
Campaigner Andrew Green of Migration Watch thinks we overestimate how beneficial the Poles have been. He says they have been good for business but not our economy as a whole.
"The question is do we import apples or apple pickers? From the point of view of society and our economy as a whole we ought to be importing the apples."
Even in Kent, expensive strawberry crops have been left to rot as there weren't the migrants to pick them.
The Poles aren't just picking apples or cleaning floors. There are many thousand in skilled jobs and their departure could mean whole businesses packing up and following them.
One third of the staff at Axis Electronics, which makes circuitry at its Bedfordshire factory, are Polish. Without them, managing director Phil Innes says the company would have opened a factory abroad.
"It's not something we wanted to do but we would have struggled to recruit locally for the growth we have been through."
Mr Green says businesses have taken the easy option and not invested in local workers enough. "The employers are laughing all the way to the bank. They've got cheap, flexible, over-qualified, motivated workers. But it's bad for the low paid, it's pretty much neutral for the rest of us."
The estimated million Poles who have made it to Britain since 2004 have allowed the UK to paper over fundamental problems, particularly a lack of skilled workers. David Frost, chief executive of the British Chambers of Commerce, says it's not just the skills that make Poles attractive to employers.
Migrants often do work few Britons are prepared to
"There is an attitude and work ethic problem in certain parts of the UK where people do not see the need or have the desire to work."
On Polish expat websites, the hot topic is who is going back and when. While many migrant workers will stay for a lot longer, if not for good, one of the key factors is the exchange rate.
The Polish zloty has strengthened against the pound since 2004 - then £1 would buy 7 zloty and today it's about 4.8, which means less money to send home. "We are quite confused, we don't know what we should do," says Kasia Kopacz, editor of the Polish Times.
"If the exchange rate gets much worse, I think 70% of Polish people would go back, for sure."
The Investigation is broadcast on BBC Radio 4 on Thursday, 27 March at 2000 GMT and afterwards on the Listen Again website.